秦岭-祁连结合部位早古生代埃达克岩的发现及其造山作用意义   总被引：1，自引：0，他引：1  

孟祥舒  何艳红  陈亮  务磊 《地质学报》2017,91(12):2679-2696

阎家店闪长岩体位于北祁连造山带东段,是秦-祁构造结合部位最大的早古生代复合闪长岩体,主要岩性为石英闪长岩-闪长岩。早期研究显示阎家店闪长岩体北部样品的测年结果为~440Ma,是以红土堡基性火山岩为代表的弧间裂谷(或初始弧后盆地)在中晚奥陶世向北俯冲形成的岛弧侵入岩体。区域资料显示阎家店闪长岩自北向南岩体逐渐发育平行定向构造,具有糜棱结构,片麻状构造。南部糜棱岩化闪长岩LA-ICP-MS锆石U-Pb定年结果显示其形成于418±3.2Ma。主微量元素地球化学特征显示其与埃达克岩地球化学特征一致,具有高Si O2,Al2O3,Na2O和Sr,低Yb和Y以及高Sr/Y和(La/Yb)N比值,无或微弱的Eu异常。低Na/K,Nb/U和Ce/Pb比值以及负的εHf(t)值表明阎家店闪长岩体主要起源于壳源物质的部分熔融。较高的Y/Yb和Ho/Yb以及Nb/Ta暗示其源岩已经转变为榴辉岩相物质。高密度的榴辉岩相基性下地壳由于重力不稳定性拆沉进入地幔,受地幔橄榄岩交代导致了阎家店闪长岩体南部样品的高Mg O含量以及Mg#。因此,自~440Ma至~418Ma秦岭-祁连结合部位的地壳在不断地加厚,~418Ma的阎家店闪长岩形成于俯冲后碰撞造山阶段,其动力学背景和时限与北祁连构造带一致。  相似文献   

小兴安岭西北部与永新金矿有关岩浆岩的年代学和地球化学及成矿构造环境     

李成禄  徐文喜  于援帮  李光辉  李胜荣  袁茂文  李士胜  徐国战 《现代地质》2017,31(6):1114

永新金矿是近年发现的大型蚀变岩型脉状金矿床,闪长玢岩脉等与金矿脉相互穿切并侵入于上盘龙江组火山岩中。锆石LA ICP MS U-Pb测年显示,龙江组安山岩结晶年龄为(1137 ± 18)Ma,闪长玢岩结晶年龄为(1148 ± 19)Ma,均形成于早白垩世晚期。二者钠钾含量变化相对较大,相对富铝富铁、钙镁含量中等,从火山岩到脉岩表现为钙碱性向碱性系列过渡特征。火山岩、脉岩与矿石的稀土元素配分曲线有很好的一致性,矿石稀土含量低于岩石。岩石微量元素总体显示Zr、Hf、Nd、U等明显富集,而Nb、Ta、Th、P、Ti等明显亏损。在Sr/Y-Y和(La/Yb)N-(Yb)N图解中,所有样品均落入经典岛弧岩石范围;在Nb-Y、Ta-Yb的构造环境判别图中均处于火山弧岩浆岩区,在(La/Yb)N-δEu变异图上落在壳-幔型岩浆范围。结合矿床稳定同位素及区域金矿时空分布规律等综合特征,认为永新金矿的形成与早白垩世古太平洋板块俯冲所引发的(火山)岩浆活动有关。  相似文献   

Zircon U-Pb geochronology and geochemistry of diorite dikes from Nancha ore deposit in Tonghua area of Jilin and its geological significance     

WU Qiong  SUN Fengyue  WANG Li  LIU Jinlong  TIAN Lidan  WANG Fei 《世界地质(英文版)》2017,(1)

The authors presented geochronology and geochemical data of diorites from Nancha gold deposit in Tonghua region,with the aim to constraining its formation age,magma source and tectonic setting.LA-ICP-MS U-Pb dating results of zircons from the diorites indicate that the rocks were formed in the Middle Jurassic( 171± 2 Ma,MSWD = 1.19).Geochemically,these rocks have Si O_2 concentrations of 52.52%--54.90%,K_2 O of2.14%--3.84%,Na_2 O of 3.17%--3.35%,Mg O of 7.43%--9.34% and high Mg~# of 68.57-72.57.These rocks are characterized by enrichment in large ion lithophile elements( LILE,such as K,Ba,Rb and Sr) and light rare earth elements( LREE),relatively depletion in high field strength elements( HFSE,such as Ta,Nb,Ti and Zr),and heavy rare earth elements( HREE).These characteristics suggest that primary magma of the rocks were derived from the partial melting of mantle with miner crustal contamination,which may related to partial melting of mantle wedge by addition of sediment melt from subducting oceanic crust.Based on former and present studies,the authors consider that the Nancha ore deposit high-Mg diorites were formed in compressional structural setting which is similar to volcanic arc.It could be related to the subduction of the Paleo-Pacific plate beneath the Eurasian continent.  相似文献   

新疆包古图Ⅲ号岩体岩石学和锆石SHRIMP年代学研究   总被引：5，自引：1，他引：4       下载免费PDF全文

魏少妮  程军峰  喻达兵  郑波  朱永峰 《地学前缘》2011,18(2):212-222

野外地质观测表明,包古图Ⅲ号岩体由两部分组成（北部的Ⅲ 1和南部的Ⅲ 2）,Ⅲ 1的岩性为花岗闪长岩和石英闪长岩,Ⅲ 2的岩性为石英闪长岩、闪长岩和少量辉石闪长岩。挑选Ⅲ 1岩体中部新鲜石英闪长岩样品,测得其锆石SHRIMP年龄为(313±3）Ma。包古图Ⅰ、Ⅱ、Ⅲ 1、Ⅳ、Ⅴ号岩体具有相似的形成时间,集中在310~325 Ma,成矿作用发生在岩浆演化的晚期（316~310 Ma）。  相似文献   

新疆大黑山地区双庆铜矿北岩体地球化学特征及其构造环境     

余吉远  李建星  孟勇  郭琳  王建强  王健 《矿物岩石地球化学通报》2009,28(4):377-383

新疆哈密大黑山地区双庆铜矿北岩体的岩石类型主要为花岗闪长岩,少数为英云闪长岩,SiO2含量平均为74.18%,K2O/Na2O值平均为1.52,相对富钾,岩石属高钾钙碱性系列,岩石酸、碱度与同类岩石平均值相当,而镁铁组分低于平均值,显示岩石偏酸性,与碰撞构造环境形成的花岗岩特征类似。Al2O3含量较高,平均为12.83%,A/CNK平均为1.05,呈轻微铝过饱和。岩石总体上相对富集大离子亲石元素,亏损高场强元素。稀土元素总量较高,平均为202.12×10^-6,（La/Yb）N=6.32-19.57 1,（La/Sm）N=3.54-4.88 1,为轻稀土富集型。δEu=0.29~0.5,为明显的铕负异常。经多种相关图解判别,岩石属S型花岗岩,其构造环境相当于碰撞挤压环境花岗岩类。锆石颗粒U-Pb测年结果显示,源岩的岩浆成因锆石形成年龄为1058 Ma,相当于中元古代。本文指出该岩体为南天山地块与中天山地块碰撞后期长城系变质岩部分熔融的产物,是Rodinia超大陆的形成在该区的反映。  相似文献   

Geochemical Characteristics of Intrusive Rocks, Southeastern Mindanao, Philippines: Implication to Metallogenesis of Porphyry Copper-gold Deposits     

Leilanie Osano Suerte  Akira Imai    Sho Nishihara 《Resource Geology》2009,59(3):244-262

This paper describes petrologic and geochemical characteristics of intrusive rocks associated with porphyry copper deposits in south-eastern Mindanao, the Philippines, where the Kingking deposit is located. Intrusive rocks at the Kingking deposit, are classified into biotite-bearing diorite porphyry, hornblende diorite porphyry and diorite porphyry. Intrusive rocks in other areas in south-eastern Mindanao, including Batoto, Bukal, Maragusan, Masara, Amacan and Sumlog, are hornblende diorite porphyry and hornblende quartz diorite. They are adakitic in Sr/Y-Y diagram, but not in La/Yb-Yb diagram due to relatively low REE contents. The magmas are oxidizing as suggested by the high X_Mg of mafic silicate phenocrysts and SO₃ contents of microphenocrystic apatite. An Oligocene-Miocene diorite intrusive complex formed by calc-alkaline, hydrous, oxidizing magma is considered to be associated with porphyry-type copper-gold mineralization.  相似文献   

Preliminary stratigraphic and structural architecture of Bhutan: Implications for the along strike architecture of the Himalayan system   总被引：5，自引：0，他引：5  

Nadine McQuarrie  Delores Robinson  Sean Long  Tobgay Tobgay  Djordje Grujic  George Gehrels  Mihai Ducea 《Earth and Planetary Science Letters》2008,272(1-2):105-117

High-precision in-situ ion microprobe (SIMS) oxygen isotope analysis of zircons from two diorite intrusions associated with the late Caledonian Lochnagar pluton in Scotland has revealed large differences in the degree of heterogeneity in zircon δ¹⁸O between the diorites. Zircon crystals from the Cul nan Gad diorite (CnG) show a unimodal distribution of oxygen isotope values (δ¹⁸O = 6.0 ± 0.6‰ (2σ)) and no or only minor grain-scale variation. Those from the Allt Darrarie diorite (AD1) show a large range in δ¹⁸O and an apparent bimodal distribution with modes of 6.6 ± 0.4‰ and 7.3 ± 0.4‰. Variations of up to 1.2‰ occur between and within grains; both an increase and decrease in δ¹⁸O with zircon growth has been observed. The δ¹⁸O composition of growing zircon can only change if open-system processes affect the magma composition, i.e. if material of contrasting δ¹⁸O composition is added to the magma. The variability in AD1 is interpreted to represent a cryptic record of magma mixing. A ‘deep crustal hot zone’ is a likely site for generation of the dioritic magmas which developed by mixing of residual melts and crustal partial melts or by melting of mafic lower crustal rocks. The overall small number of zircons with mantle-like δ¹⁸O values (5.3 ± 0.6‰ (2σ)) in the Lochnagar diorites is largely the product of crustal differentiation rather than crustal growth.

The δ¹⁸O of quartz from the CnG and AD1 diorites shows only minor variation (CnG: 10.9 ± 0.5‰ (2σ), AD1: 11.7 ± 0.6‰ (2σ)) within single populations, with no evidence of mixing. Quartz–zircon isotopic disequilibrium is consistent with later crystallisation of quartz from late magmatic fluids, and in case of the AD1 diorite after the inferred magma mixing from a homogenised, higher δ¹⁸O melt.

High-precision SIMS oxygen isotope analysis of zircon provides a new approach to identifying and resolving previously undetected early-stage magma mixing and constraining the compositions and origins of the component magmas. A combination of zircon, quartz and whole-rock data has proven to be a powerful tool in reconstructing the petrogenetic evolution of diorite from early crystallisation to late alteration.  相似文献   

Petrogenesis of Shangyu gabbro-diorites in western Shandong: Geochronological and geochemical evidence   总被引：10，自引：0，他引：10  

ChengHai Yang  WenLiang Xu  DeBin Yang  Wei Wang  WeiDe Wang  JinMin Liu 《中国科学D辑(英文版)》2008,51(4):481-492

Chronology and geochemistry of the Shangyu gabbro-diorite in western Shandong were studied to understand their petrogenesis and the nature of the Mesozoic lithospheric mantle. The Shangyu intru-sion is mainly composed of a suite of gabbro-diorite. Zircons from the intrusion display eu-hedral-subhedral in shape and have high Th/U ratios (1.23―2.87), implying their magmatic origin. LA-ICP-MS zircon U-Pb dating results for two samples indicate that they were formed in the Early Cre-taceous, yielding weighted mean 206Pb/238U ages of 129±1Ma and 134±2Ma, respectively. Except for early cumulate such as sample QT-19, their SiO2 and MgO contents range from 50.12% to 56.37% and from 3.52% to 6.37%, respectively. Moreover, the gabbro-diorites are characterized by high Mg# (0.54―0.63), enrichment in Na (Na2O/K2O ratios more than 1), Cr (73×10-6―217×10-6) and Ni (34×10-6―241×10-6), and intensive enrichments in light rare earth elements (LREEs) and large ion lithophile elements (LILEs) and depletion in high field strength elements (HFSEs). Their initial 87Sr/86Sr ratios and ε Nd(t) values range from 0.70962 to 0.71081 and from-16.60 to-13.04, respectively. Taken together with the Early Creta-ceous high-Mg diorites and the mantle xenoliths from the Tietonggou and Jinling as well as basalts from the Fangcheng and Feixian, it is suggested that the primary magma for the Shangyu gab-bro-diorites should be derived from the enriched lithospheric mantle intensively modified by conti-nental crust. The Sr-Nd-Pb isotopic compositions for the Early Cretaceous high-Mg diorites in western Shandong display a trend of spatial variations, i.e., initial 87Sr/86Sr, 207Pb/204Pb and 208Pb/204Pb ratios de-creasing and ε Nd(t) values increasing from southeast to northwest in western Shandong, which is con-sistent with the tectonic model that the Yangtze Craton subducted beneath the North China Craton oriented in north-west direction in the Early Mesozoic.  相似文献   

Geochemical variation in the Penmaenmawr intrusion (North Wales)     

W. E. TREMLETT 《Geological Journal》1997,32(2):173-187

To determine the pattern of geochemical variation within the Penmaenmawr intrusion, 41 rocks were analysed for major oxides and 15 minor elements. The results indicate pulsational emplacement of sheets of magma from a parental body at depth undergoing crystallization differentiation. These sheets now strike NE–SW and dip southeastward. The resultant intrusion shows a range of SiO₂ contents from 57·3% to 65·6% (H₂O-free). Geochemical evidence suggests that it was derived from an intermediate parental magma and is possibly related to parts of the Conwy Rhyolite Formation. © 1997 John Wiley & Sons, Ltd.  相似文献   

克拉通破坏型金矿成矿机制:吉南板庙子金矿床闪长玢岩与重晶石流体包裹体、H-O-S同位素证据     

陈煜嵩  董晓杰  刘正宏  贾振杨  于晓飞  吴玉诗  王海建 《岩石学报》2020,36(8):2537-2557

克拉通破坏对于华北克拉通中生代的成矿作用有着深刻的影响。相对于胶东矿集区,其他克拉通破坏型金矿矿集区的研究程度相对较低,尤其是位于华北克拉通东北部的吉南矿集区更是缺乏典型矿床的研究。本文对华北克拉通东北部吉南矿集区板庙子金矿区出露的闪长玢岩进行了岩相学、年代学及地球化学研究,同时对成矿Ⅲ阶段的重晶石矿物进行了流体包裹体、H-O-S同位素组成分析。通过LA-ICP-MS锆石U-Pb定年,在具有明显振荡环带的岩浆锆石中获得133.3±0.9Ma加权平均年龄,表明闪长玢岩的侵位时代为早白垩世;同时根据锆石CL图像下极弱的阴极发光特征识别出一组加权平均年龄为130.6±1.0Ma的热液锆石,说明岩浆侵位结晶后遭受热液蚀变改造,由此限定了板庙子金矿床的成矿时代为早白垩世。闪长玢岩地球化学特征显示亏损重稀土元素(HREEs)和Y,富集Sr,具有高钾钙碱性,Mg# 60,Na2O/K2O 1,表现埃达克质岩石特征,其岩浆来源于拆沉下地壳部分熔融,并与地幔橄榄岩反应;富集轻稀土元素(LREEs),以及亏损Nb、Ta、P、Ti等高场强元素(HFSEs)。结合区域的岩浆活动资料,表明该闪长玢岩形成于古太平洋板块俯冲作用相关的强烈伸展构造背景。重晶石矿物H-O同位素组成表明成矿流体来源于岩浆水、建造水和变质水的混合;重晶石矿物S同位素表明成矿物质来源于大洋水和海相蒸发岩。综合板庙子金矿成矿时代、成矿构造背景以及成矿流体/物质来源的特点,提出板庙子金矿属于克拉通破坏型金矿,并阐述了古太平洋板块对欧亚大陆的俯冲作用及其在早白垩世引起的拆沉作用是克拉通破坏型金矿成矿机制的关键  相似文献